Foldable ladder

ABSTRACT

A foldable ladder having rungs pivotally connected to the side rails, allowing the side rails to pivot from a position wherein the siderails are coplanar to the rung to a support position wherein the side rails are normal to the rungs.

This is a continuation-in-part of application Ser. No. 08/530,039 filedon Sep. 19, 1995, now abandoned.

FIELD OF THE INVENTION

This invention relates to a ladder and, in particular, to a ladder whichcan be folded for storage.

BACKGROUND OF THE INVENTION

Foldable ladders are known which can be folded for storage in smallspaces such as trunks of cars or closets. These ladders generally allowa ladder to be folded to about 36 inches in length. Such ladders areextended into straight, rigid form for use. Foldable ladders are oftendangerous in that they can move between a rigid position and acollapsible position relatively easily. In addition, the folding natureof the ladders can render them of insufficient strength, when extended,to support the weight of a person.

Any ladder construction should be as simple as possible, to cause thecost of the ladder to be reasonable.

SUMMARY OF THE INVENTION

A ladder is provided which can be folded for storage and extended intorigid form for use. The inventive ladder is resistant to inadvertentcollapse during use and is of sufficient strength to maintain its rigidform while supporting weight.

According to a broad aspect of the present invention there is provided aladder comprising a pair of side rails and a plurality of rungs, apivotal attachment being positioned between each rung and each of theside rails such that the side rails are free to rotate from positionssubstantially coplanar with the rungs to positions defining a planesubstantially normal to the rungs to support the rungs, the pivotalattachment between the rungs and side rails being disposed to permitrelative rotation of the side rails not more than 90° from the positionsubstantially coplanar to the rungs, and the side rails being formed insegments pivotally attached at their ends such that the side rails canbe folded into an accordion arrangement.

DESCRIPTION OF THE INVENTION

The present inventive ladder can be folded into an accordion arrangementby having side rails formed as segments which collapse about pivotalconnections disposed along the side rails. The pivotal connections arespaced longitudinally along the side rails and in correspondinglocations on each side rail so that the two side rails can foldsimultaneously. The pivotal connections are of any suitable type.Preferably, pivotal connections are provided having a suitable toleranceto accommodate weight placed on the ladder. In one embodiment thepivotal connections are in the form of double hinges. Double hingesallow ease of manufacture and strengthen the ladder. The double hingescan be formed by placing a u-shaped member between abutting ends of theside rails. The double hinges can alternatively be formed by placing apair of links between the ends. Where the rail segments are hollow,plate or block inserts formed of suitable material, such as for example,steel or plastic, can be used to reinforce the pivotal connections. Ithas been found that a plastic insert acts to retain the tightness of thepivotal connection over a greater period of time, as compared to steel,and is therefore preferred.

In a preferred embodiment, the side rails are formed as two foot longsections with a single hinge at each end. The sections are manufacturedin one piece by molding a high strength material such as plastic, fibrereinforced plastic or injectable metals. A preferred length for the siderail segments is twenty four (24) inches, however a twelve (12) inchlength can be used in some embodiments. The hinges at the ends of theside rails in this preferred embodiment are formed to join the abuttingends of the rails directly. In a preferred embodiment, the hinges areformed as a plurality of ribs extending outwardly and upwardly from theends of the segments. Apertures are disposed through the ribs foraccepting a pin about which the segments can pivot.

The segments of the side rails are free to collapse about the pivotalconnections when the ladder is disposed in a flat position wherein therungs and side rails are in a single plane. When the ladder is preparedfor use, the side rails are rotated about 90° to each define a planenormal to the plane of the rungs. As such the side rails are placed intoabutting relation with the front or back of the rungs. In such anarrangement, the corresponding hinges of the side rails are in opposingposition such that the segments of the side rails are prevented fromcollapsing about their pivotal connections to fold the ladder. Therotation of the side rails about the rungs is provided by pivotalconnections positioned between the side rails and the rungs. The pivotalconnections are positioned such that the side rails can rotatesubstantially only about 180° between abutting relation on the frontface through the plane defined by the rungs and into abutting relationwith the back face of the rungs. In a preferred embodiment, pivotalconnections are provided which permit the rotation of the side railssubstantially only about 90° in opposite directions relative to therungs to a selected one of the back or front of the rungs, such thatinadvertent placement of the pivotal connections of the side rails intoposition where they can collapse is prevented. Rotation of the siderails beyond 90° is prevented in a first direction by the abutment ofthe side rails against the rungs. Rotation in the second direction isprevented by means associated with the pivotal connection such as by anabutting wall or flange. Thus, inadvertent rotation of the side railsinto collapsible position by torsional forces during use is prevented.Since the rails rotate in opposite directions to abut the rungs, oneside rail will always, by abutment against the rungs, resist thetorsional force which tends to rotate the side rails into collapsibleposition.

The hinges for connecting the side rails to the rungs preferably areformed integral with side rail and rungs to facilitate manufacture.

In a preferred embodiment, also to prevent inadvertent rotation of theside rails into a collapsible position, a lock is provided between atleast one rung and a side rail. In one embodiment, the lock is a flange,extending out from the side rail, which is engaged by a sliding sleeveon the rung. In another embodiment, the lock is a hooked clip extendingout from the side rail which engages in an indentation formed on therung.

The ladder is preferably formed of lightweight and high strengthmaterial such as polymeric, fibre reinforced polymeric or injectablemetal materials. In a one embodiment, the side rails and rungs areformed of extruded aluminum. In this embodiment, the side rails andrungs are preferably formed to have inner longitudinally extendingchannels for engaging adapters useful for reinforcement of the pivotalconnections. In another embodiment, the ladder is molded from polymericmaterials such as structural foam ABS.

BRIEF DESCRIPTION OF THE DRAWINGS

A further, detailed, description of the invention briefly describedhereinbefore will follow by reference to the following drawings ofspecific embodiments of the invention. These depict only typicalembodiments of the invention and are therefore not to be consideredlimiting of its scope. In the drawings:

FIG. 1A shows a side view of one embodiment of a ladder according to thepresent invention in folded arrangement;

FIG. 1B shows a side view of the ladder of FIG. 1A in flat arrangement;

FIG. 1C shows a side view of the ladder of FIG. 1A in position for use;

FIGS. 2A, 2B and 2C show end views of the ladder as shown in FIGS. 1A,1B and 1C, respectively;

FIG. 3 shows a plan view of the ladder as shown in FIGS. 1C and 2C.

FIG. 4 shows a plan view of the hinge portions of an embodiment of aladder of the present invention, partly in section;

FIG. 5 shows a perspective view of a hinge useful in the presentinvention;

FIG. 6 shows a perspective view of another hinge useful in the presentinvention;

FIG. 7 shows a perspective view of another hinge useful in the presentinvention;

FIG. 8A shows an end view of a ladder of the present invention having alock arrangement, the ladder being in a flat arrangement;

FIG. 8B shows an end view, partly in cross section, of the ladder ofFIG. 8A in a position for use.

FIG. 9A shows a side view of another embodiment of a ladder according tothe present invention in folded arrangement;

FIG. 9B shows a side view of the ladder of FIG. 9A in a flatarrangement;

FIG. 9C shows a side view of the ladder of FIG. 9A in a position foruse;

FIG. 10 is a sectional view along line 10--10 of FIG. 9B;

FIG. 11 is an exploded view of a ladder according to the presentinvention with a lock arrangement; and

FIG. 12 is a schematic view of an end view of the lock arrangement ofFIG. 11.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1A, 1B, and 1C and corresponding FIGS. 2A, 2B, 2C and3, the inventive ladder can be arranged between a folded position asshown in FIGS. 1A and 2A, for storage, and an extended, rigid positionfor use as shown in FIGS. 1C, 2C and 3.

The side rails 10 of the ladder are formed as segments 12a, 12b, 12c.Segments 12a, 12b, and 12c are pivotally attached at their ends by meansof double hinge arrangements 11a, 11b. The double hinge arrangements areformed by intermediate members 13a, 13b, which attach segments 12a, 12b,and 12c such that they are able to be rotated simultaneously about pivotpoints 14a, 14a', 14b, 14b', 15a, 15a', 15b and 15b'. (Pivot points 14a,14a', 14b, 14b' are disposed behind pivot points 15a, 15a', 15b, 15b' inFIGS. 1A-1C). A plurality of rungs 16a, 16b, and 16c (shown in phantomin FIGS. 1A, 1B and 1C) are pivotally connected between side rails 10 bymeans of single hinges 18 disposed at each end of each rung. Any numberof segments and rungs can be used in combination.

To prepare the ladder for use, side rail segments 12a, 12b, and 12c areunfolded and arranged longitudinally into flat arrangement, as shown inFIGS. 1B and 2B, such that the side rails and the rungs are insubstantially the same plane, as indicated in phantom at 19. In thisposition, segments 12a, 12b, 12c are free to rotate about pivot points14a, 14a', 14b, 14b', 15a, 15a', 15b and 15b'.

To render the ladder suitable for use in supporting weight, side rails10 are rotated 90° in opposite directions about hinge connections 18such that the side rails are in parallel planes 20, 20a normal to plane19, as shown in FIGS. 1C, 2C and 3. When side rails 10 are rotated inthis way the segments on opposite side rails could only fold if theywere able to pivot in opposite directions as indicated by arrows a (FIG.3). Thus, the side rails will be maintained rigid as corresponding pivotpoints, eg. 14a and 15a, 14a' and 15a', 14b and 15b and 14b' and 15b',on opposite side rails, cannot fold simultaneously.

The ladder is rendered into a folded position by reversing the unfoldingoperation.

Referring to FIG. 4, a plan view, partially in section, of a portion ofthe ladder in flat position is shown. Side rail segments 12a and 12b aresubstantially identical in construction and are connected by doublehinge 114. Referring also to FIG. 5, the preferred hinge connectionincludes a u-shaped member 120 which extends between abutting ends ofsegments 12a, 12b. The edges of member 120 are curved to permit rotationof the hinge. Member 120 is formed of material such as aluminum or steelhaving sufficient strength to withstand the force of segments 12a, 12bacting thereon during use of the ladder. Preferably member 120 is formedof 3/8" to 1/2" thick aluminum. Member 120 is pivotally connected to anend of each of segments 12a and 12b.

Preferably, as shown, plate members 122 are inserted between member 120and each segment 12a and 12b. Members act as a rigid extension ofsegments 12a and 12b, respectively. Plates 122 are pivotally attached tomember 120 through pivot points 124, such as rivets (as shown) or a pin.The ends of the plates are curved in plan view to permit rotation aboutthe pivot points 124. Plates 122 are rigidly attached to side railsegments by fasteners 127, such as rivets as shown. Plates 122 aresecured to side rail segments 12a, 12b by insertion into channels 125formed in the side rails (see FIG. 5). Channels 125 are defined byflanges 126 extending from the inner surface of side rail segments 12a,12b.

Flanges 126 can be formed on the side rails by extrusion. Plates 122 areformed of material, such as for example steel, of sufficient strength towithstand stresses about the pivotal connections during use. By use ofplates 122, the side rails and rungs can be formed of thin material,such as 1/16" thick aluminum while the pivotal connections arereinforced by the plates.

Referring to FIG. 6, in another hinge connection a block insert 150 isused in place of the plates 122 of FIG. 5. Block insert 150 is formed tohave a first end 150a which fits into an end of a side rail 12 and asecond end 150b which extends out from side rail 12. Rivets 152 extendthrough apertures in side rail 12 to engage insert 150. A bore 156extends through end 150b of insert 150 to accommodate a pin 162, whichforms the pivotal connection of the double hinge. Insert 150 ispreferably injection molded from a suitable plastic, such as nylon.

A pair of links 158 can be used in place of the member 120 of FIG. 5 toform the double hinge joining side rail segments. Links 158 are attachedat the sides of the side rail and extend between abutting ends of theside rail segments (for example 12). The edges of links 158 are curvedat a first side 160 to permit rotation of the hinge in one direction.Pin 162 is mounted through apertures 164 in links 158 and bore 156 ininsert 150 to provide the pivotal connection of the double hinge. Links158 are pivotally attached to another side rail segment (not shown), asdescribed, through apertures 166. Links are preferably formed of 3/8" to1/2" thick aluminum.

The plates 122 and insert 158 shown in FIGS. 5 and 6, respectively, areinterchangeable as are the member 120 and the pair of links 158. Anysuitable combination of these elements can be used in the same ladder,if desired.

Referring back to FIG. 4, a bearing member 130 is attached to side railsegment 12b for pivotal connection to rung 16. Bearing member 130 isattached to side rail 12b by means of rivets 132 or other suitable meanssuch as welds or threaded fasteners. The pivotal connection to rung 16is through a pair of plates 134 inserted at each end of rung 16. Plates134 have apertures 136 for accepting rivets 138 for rigid attachment torung 16 and apertures 139 for accepting a pin 140 for attachment tomember 130. Rung 16 has formed on its inner surface upstanding flanges142 which define channels 144 for insertion of plates 134. Plates 134can alternately or additionally be held in position in rung 16 by anysuitable means, such as means of adhesives, welds or fasteners.

Referring to FIG. 7, an alternate embodiment of a pivotal connectionbetween a rung 16 and a side rail segment 12 is shown. A insert 242 fitswithin an end of rung 16 for connection to bearing member 230. A bore244 formed through insert 242 aligns with apertures 246 of member 230for accepting a pin (not shown). Insert 242 is preferably formed ofinjection molded plastic, such as nylon. Preferably, insert 242 ismolded with channels 245 which engage ribs 247 on rung 16 to increaserigidity of the structure.

To facilitate rotation of the side rails into position for use, in apreferred embodiment an elastic cord, indicated by phantom line 250, isinserted through rung 16 to extend at each end in groove 252 of insertfor attachment, under tension, to side rail segment 12, generally at254. The tension of elastic cord 250 acts to cause the side rail to bedrawn up into position for use when the ladder is unfolded into a flatposition.

In the preferred embodiment, rung and side rail pivotal connections aredisposed to rotate only about 90° with respect to each other. Referringto FIG. 7, for example, insert 242 is formed at its end to allowrotation only in one direction, while rotation in the alternatedirection is prevented by a corner portion 248 formed on insert 242.Rotation can also be prevented by providing other means such as a sidewall on member 230. Such means act to prevent the side rails from beingrotated into collapsible position during use.

Referring to FIG. 8A and 8B, to further prevent the inadvertent rotationof the side rails into collapsible position during use, a lock ispreferably provided between at least one rung 16 and a side rail segment12. A suitable lock includes a sleeve 372 which is slidingly engaged onrung 16 and a flange 374 engaged on side rail segment 12. Preferablyflange 374 is formed as a projection on bearing member 330. Flange 374extends out from the side rail and is positioned such that it does notinterfere with the folding of the ladder. Flange 374 is furtherpositioned such that it will overlie rung 16 when side rail segment 12is rotated about 90°, for use, as shown in FIG. 8B. In this position,sleeve 372 can be moved along rung 16 into position over flange 374, toengage flange 374 and lock side rail segment 12, and thereby the entireside rail, into position relative to rung 16. A spring actuated pushbutton 380 is preferably provided within rung 16 to extend partiallythrough an aperture 382 formed in rung 16 to hold sleeve 372 in lockingposition over flange 374. To release sleeve 372 from locking positionover flange 374, push button 380 is pressed and sleeve 372 is movedalong rung 16. The side rail is then free to rotate into collapsibleposition.

Referring to FIGS. 9A, 9B, 9C another embodiment of the presentinvention is shown. The ladder includes side rails 421 formed ofsegments 422a, 422b, 422c. The segments are formed as I-beams of anysuitable material. As an example, suitable dimensions for a segmentformed of fibre-glass reinforced nylon are: height 3", width 1.2" andweb thickness of 0.1". In another example, the side rail has a webthickness of 0.25" and is formed of structural foam ABS plastic. Thesegments are joined at their abutting ends by means of a single hingearrangement 425a, 425b. A plurality of rungs 426a, 426b, 426c (shown inphantom in FIGS. 9A and 9B) are pivotally connected between side rails421 by means of single hinges 428 disposed at each end of each rung426a, 426b, 426c. The ladder of this embodiment is prepared for use inthe same way as that described in relation to FIG. 1A-1C.

Referring also to FIG. 10 , side rail segments 422a and 422b areconnected by single hinge 425a. Single hinge 425a includes a hinge pin429 about which the segments pivot. Ribs 430a-430c extend out from theends side rail segment 422a at the end thereof and have alignedapertures 435 formed therethrough segment 422b has similar ribs 430a',430b' and 430c' with apertures 435'. Hinge pin is disposed throughapertures 435, 435'. The edges of the ribs are curved to permit rotationabout the pin. To permit segments 422a and 422b to be aligned alongtheir length, ribs 430a-430c on segment 422a are offset from ribs430a'-430c' on segment 422b. Preferably the ribs are formed integralwith the segment, as shown. Alternatively, the ribs can be formedseparately and attached to the segments by any suitable means. To permitaligned connection of all adjacent segments and ease of manufacture eachsegment is formed with a first defined end and a second defined end. Thefirst defined end on a segment is shaped to hinge to any second definedend on another segment. As will be understood other arrangements andnumbers of ribs can be used to obtain attached segments which can bepivoted relative to each other from a position in which theysubstantially abut to a position in which one segment is folded over theother in an accordance arrangement.

Rung 426b is pivotally attached to segment 422b by a pin 440 whichpasses through aligned apertures 442 formed in a bearing member 444 onsegment 422b and an alignable aperture 446 formed through rung 426b.Bearing member 444 is preferably formed integral with the segment.

Referring to FIG. 11, another embodiment of the invention is shownwherein rung 526 has a plurality of ribs 570 formed on its ends. Eachrib has one aperture 571 formed therethrough which is aligned with theapertures on the other ribs. Rail segment 522 also has formed thereon aplurality of ribs 572 with aligned apertures 573 therethrough. Toconnect rung 526 to segment 522, ribs 570 mesh with ribs 572 and a hingepin 540 is inserted through the aligned apertures. Referring also toFIG. 12, another lock is shown for preventing the inadvertent rotationof the side rails into collapsible position during use. The lock acts atthe hinge between side rail 522 and a rung 526 and includes a lock cliphaving a base portion 580 with an aperture 581 therethrough and an armportion 582 extending from base portion 580. Arm portion includes a hook583. Arm portion 582 is preferably shaped, such as by bending, to extendin a plane offset from the plane defined by the base.

Clip is secured to the hinge to be locked by use of hinge pin 540 whichis inserted through aperture 581. An enlarged portion on hinge pin 540prevents the pin from passing through aperture 581. The clip is securedto remain in position with arm portion 582 extending out substantiallyorthogonally from the plane of the rail segment. Base portion 580 isshaped to prevent rotation of clip about hinge pin 540. A spring 585 ismounted at the opposite end of the hinge pin 540 and a bolt 586 issecured on a threaded portion 587 of hinge pin to retain spring 585 onhinge pin 540. Spring 585 acts between the hinge and bolt 586 to pullhinge pin 540 down such that the clip is maintained against the hinge.

The clip is mounted on the hinge such that the plane of defined by thearm portion is positioned toward the rung and hook portion 583 alsoextends towards the rung. Rung 526 has formed on its surface anindentation 588 shaped and positioned to accept arm portion 582 and hook583. The clip acts to lock the side rails in a position wherein theyextend out substantially orthogonally from the plane of the rungs.Spring 585 normally draws the clip toward the hinge. When rung 526 isrotated to a position orthogonal to the plane of the rail segment asshown by arrow B, arm portion 582 of the clip is forced up out of theway of rung 526 by compression of spring 585. The clip rides over thesurface of rung 526 until it is drawn into indentation 588 in the rung.Spring 585 maintains arm portion 582 including hook 583, securely inindentation 588 which prevents further rotation of the rung.

When it is desired to return the ladder to a foldable position, forcecan be applied to hinge pin 540 to compress spring 585 and cause armportion 582, including hook 583, to be displaced from indentation 588.Rung 526 is then free to be rotated.

Preferably, a guide flange 589 is formed on base portion 580 to maintainthe clip in position and to guide the movement of the clip away from andtoward the hinge during compression of spring 585. Guide flange 589 isformed to fold around and ride along an end wall 590 of the segment 522.

Preferably, hook 583 is tapered toward its end to facilitate the clipsability to ride over the surface of the rung when moving into thelocking position. In a preferred embodiment, the clips are placed on theladder such that they engage the upper surface of the rungs. In thisway, should a person using the ladder step on the lock portion, thisonly causes the clip to be further forced into the indentation of therung.

It will be apparent that many other changes may be made to theillustrative embodiments, while falling within the scope of theinvention, and it is intended that all such changes be covered by theclaims appended hereto.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A ladder comprising apair of side rails and a plurality of rungs, a hinge positioned betweeneach rung and each of the side rails such that the side rails are freeto rotate from positions substantially coplanar with the rungs topositions defining a plane substantially normal to the rungs to supportthe rungs, the hinges between the rungs and the side rails beingdisposed to permit relative rotation of the side rails not more than 90°from the position substantially coplanar to the rungs and each hingeincluding a plurality of ribs formed integral with the side rail andextending outwardly from a side thereof and a plurality of ribs formedintegral with the rung at an end thereof, the ribs each having anaperture therethrough aligned with the apertures of adjacent ribs, theribs of the rung being meshed with the ribs of the side rail with theirapertures in alignment and a hinge pin extending through the alignedapertures, and the side rails being formed in segments attached at theirends by segment hinges such that the side rails can be folded into anaccordion arrangement, the segment hinges each including a plurality ofend ribs formed integral with the segments and extending outwardly froman end thereof each end rib having an aperture therethrough aligned withthe apertures of adjacent end ribs, the end ribs of the segments beingmeshed with their apertures in alignment and a hinge pin extendingthrough the aligned apertures, wherein an elastic cord is connectedbetween at least one rung and each side rail adjacent the rung, theelastic cord being under tension and positioned to drive the side railsfrom the position substantially coplanar with the rung to the positionwherein each side rail defines a plane substantially normal to the rung.2. The ladder as defined in claim 1 wherein at least some of the hingesbetween the rungs and the side rails are formed to allow rotationsubstantially only about 90° from the position substantially coplanarwith the rungs towards one of a front facing side of the ladder or arear facing side of the ladder.
 3. The ladder as defined in claim 1wherein the rungs are formed to restrict rotation of the side railsabout the rungs to substantially only about 90° from the positionsubstantially coplanar with the rungs towards one of a front facing sideof the ladder or a rear facing side of the ladder.
 4. The ladder ofclaim 1 further comprising a lock for locking the ladder into anextended position.
 5. The ladder of claim 4 wherein the lock is disposedbetween each side rail and at least one rung.
 6. The ladder of claim 4wherein the lock is selected to lock between the rung and the side railautomatically when the side rail is rotated from the positionsubstantially coplanar with the rung to the position wherein each siderail defines a plane substantially normal to the rung.
 7. The ladder ofclaim 6 wherein the lock includes a hook selected to engage into anindentation when the side rail is rotated to align the hook with theindentation.
 8. The ladder of claim 7 wherein the hook is positioned onthe side rail and the indentation is positioned on the upper surface ofthe rung.
 9. A ladder comprising a pair of side rails and a plurality ofrungs, a pivotal attachment being positioned between each rung and eachof the side rails such that the side rails are free to rotate frompositions substantially coplanar with the rungs to positions defining aplane substantially normal to the rungs to support the rungs, thepivotal attachment between the rungs and the side rails being disposedto permit relative rotation of the side rails not more than 90° from theposition substantially coplanar to the rungs and the side rails beingformed in segments, each segment having a width and being pivotallyattached at their ends such that the side rails can be folded into anaccordion arrangement and a lock disposed between each side rail and atleast one rung to lock the side rail into the position defining a planesubstantially normal to the rungs, the lock being selected to lockbetween the rung and the side rail automatically when the side rail isrotated from the position substantially coplanar with the rung to theposition wherein each side rail defines a plane substantially normal tothe rung, wherein an elastic cord is connected between at least one rungand each side rail adjacent the rung, the elastic cord being undertension and positioned to drive the side rails from the positionsubstantially coplanar with the rung to the position wherein each siderail defines a plane substantially normal to the rung.
 10. The ladder ofclaim 9 wherein the lock includes a hook selected to engage into anindentation when the side rail is rotated to align the hook with theindentation.
 11. The ladder of claim 10 wherein the hook is positionedon the side rail and the indentation is positioned on the upper surfaceof the rung.
 12. The ladder as defined in claim 9 wherein at least someof the pivotal attachments between the rungs and the side rails areformed to allow rotation substantially only about 90° from the positionsubstantially coplanar with the rungs towards one of a front facing sideof the ladder or a rear facing side of the ladder.
 13. The ladder asdefined in claim 9 wherein the rungs are formed to restrict rotation ofthe side rails about the rungs to substantially only about 90° from theposition substantially coplanar with the rungs towards one of a frontfacing side of the ladder or a rear facing side of the ladder.
 14. Theladder of claim 9 wherein the segments are pivotally attached by hingesincluding a plurality of ribs formed integral with the segments andextending outwardly from an end thereof, the ribs each having anaperture therethrough aligned with the apertures of adjacent ribs and ahinge pin extending therethrough.
 15. The ladder of claim 9 wherein thepivotally attachments between the rungs and the side rails are eachhinges including a plurality of ribs formed integral with the side railand extending outwardly from a side thereof and a plurality of ribsformed integral with the rung and extending outwardly from an endthereof, the ribs each having an aperture therethrough aligned with theapertures of adjacent ribs, the ribs of the rung being meshed with theribs of the segment with their apertures in alignment and a hinge pinextending through the aligned apertures.